Typo in error string

[giorgionocera]

Hi there,
it seems that during the 4c6c593 commit, this error message was not adapted.

nois/src/select_from_weighted.rs

Line 47 in 4c6c593

.ok_or_else(|| String::from("Total weight is greater than maximum value of u32"))?;

The function works also with values that sums to u128:MAX, so x | 0 ≤ x ≤ u128 => x ≥ u32 is fine.

It is only an error message, but I'm preparing a PR for this.